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Biomedical subjects

C J Barker

Publications and source records attributed to C J Barker.

22 records · Page 2Linked to original sources
PubMed1983

Hematologic and enzymatic analysis of Ctenopharyngodon idella x Hypophthalmichthys nobilis F1 hybrids.

1. Erythrocyte counts, hemoglobin concentrations and hematocrit values were determined for diploid and triploid Ctenopharyngodon idella X Hypophthalmichthys nobilis hybrids and the parental species. 2. Comparisons of diploid and triploid hybrids with the parental species revealed low erythrocyte counts for triploids, high mean corpuscular hemoglobin values for triploids, elevated hematocrits for diploids and triploids and similar hemoglobin concentrations for all fish. 3. Alkaline phosphatase, aldolase, and lactate dehydrogenase specific activities were determined spectrophotometrically. Levels of specific activity of these enzymes in the hybrids were consistently elevated above that of the parental species. These higher levels of enzyme activities in hybrids were probably the result of a breakdown in gene regulation.

Alkaline Phosphatase↗
PubMedDate not supplied

The effect of the administration of ethanol to rats on the thermal sensitivity of transplantable tumours.

1. Long-term maintenance of rats on a diet containing ethanol did not cause compensatory changes in brain synaptic membrane lipid composition, nor was there any change in membrane lipid order as measured by steady-state fluorescence polarization of DPH. 2. The lipid composition of MC7 tumour plasma membranes was also determined in ethanol-fed and then sucrose pair-fed controls. Dietary ethanol caused no change in the composition of phospholipid classes. There was, however, a tendency for an increase in C18 fatty acids and an increase in monounsaturated at the expense of unsaturated and polyunsaturated fatty acids. There was no significant change in cholesterol content. 3. Tumour membranes from ethanol-fed rats were not different in lipid order from their pair-fed controls. Tumour membranes were, however, significantly less ordered than synaptic membranes. 4. A single heat treatment of 44 degrees C for 1 h increased the survival time of rats bearing both MC7 and D23 foot tumours. No difference in their survival was seen between ethanol-fed and sucrose pair-fed controls.

Alcoholism↗
PubMedDate not supplied

Inositol hexakisphosphate and beta-cell stimulus-secretion coupling.

Inositol hexakisphosphate (InsP6) inhibits serine/threonine protein phosphatases type-1 (PP1), type-2A (PP2A) and type-3 (PP3) in a concentration-dependent manner. Since the activity of voltage-gated L-type Ca(2+)-channels is increased by inhibition of serine/threonine protein phosphatases, this may explain trhe increased Ca(2+)-channel activity obtained in the presence of InsP6. In insulin-secreting cells, InsP6 is therefore likely to be one of the key elements modulating Ca(2+)-influx over the plasma membrane. InsP6 can also modulate insulin exocytosis in permeabilized cells. Concentrations of InsP6 above 20 microM stimulated insulin secretion at basal Ca(2+)-concentration (30 nM) and primed Ca(2+)-induced exocytosis (10 microM), both effects being due to activation of PKC. Hence, InsP6 can play an important modulatory role in the regulation of insulin exocytosis and the specific role may then be to recruit secretory granules to the site of exocytosis. The fact that some InsP6 is localised to membranes, so being topographically disposed to regulate ion channels as well as exocytosis, and that it has a rapid rate of turnover in glucose-stimulated insulin-secreting cells, suggest novel functions for InsP6 in the insulin secretory process.

Animals↗